Integrated gate drivers may comprise output stage buffers including p-type metal-oxide-semiconductor (“PMOS”) transistors for a pull-up path and an n-type metal-oxide-semiconductor (“NMOS”) for a pull-down path. In certain high power applications, a large percentage of a die area may be occupied by a driver output stage comprising two or more high-voltage transistors capable of providing robust output currents and large gate voltages. It is desirable to implement alternative output stage buffer configurations that more efficiently use the die area. In some high-voltage applications, the PMOS transistor may be several times (e.g., over 30 times) larger compared to the NMOS transistor in its specific resistance, resulting in the pull-up path occupying more die area than the pull-down path. Technological improvements in complementary metal-oxide-semiconductors manufacturing processes have led to integration of more functionality within a smaller die area. An output stage of an integrated gate driver circuit comprising NMOS transistors for both pull-up and pull-down paths are an approach that may result in a reduced die area and lower manufacturing costs.
The output stage of an integrated gate driver utilizing an NMOS transistor for the high-side switch may use a bootstrap power supply to provide the gate overdrive voltage when the high-side NMOS transistor turns on. However, since the bootstrap capacitor, during the time when the low-side switch is not active, provides gate charge to the gate terminal of the high-side switch, power supply voltage for the buffer coupled to the high-side switch, and supplements charge lost due to leakage and quiescent currents, a relatively large bootstrap capacitor may be selected to ensure sufficient gate drive for substantially higher duty-cycles. For example, it is conventional to implement the bootstrap capacitor as discrete component. But such an arrangement generally increases manufacturing cost, pin count for an integrated circuit, and size of a printed circuit board.
There is, therefore, a continued need for die area efficient integrated gate boosted driver.